Experiment study of alluvial fans formed by torrential floods

• Main Authors: Chun-chuan Wu, 吳俊銓
• Other Authors: Hsien-Ter Chou
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/52773225444095606495

碩士 === 國立中央大學 === 土木工程研究所 === 100 === Mountain floods accompanied with landslides, slope avalanches and debris flows often cause tremendous disasters to downstream residents and infrastructures. The dynamic process and deposit mechanism of alluvial fans by torrential flows is experimentally explored in this study. An acrylic flume experiment is adopted to observe the deposit progress of granular flows, deposit angle of foreset and topset, and flow patterns with a high-speed camera. The particle size (D), water discharge (Q w ), and sediment discharge (Q s ) dominates the flow patterns, and the slopes of foreset and topset mainly depend on sediment concentration (i.e., the ratio of sediment discharge to water discharge). The slope of topset increases with increasing sediment concentration. The velocity profiles of the flowing layer are explored by using particle image velocimetry (PIV). The velocity profiles in the flowing layer depict SSH rheology when the free surface is equal to or slightly higher than granular-flow surface. When the free surface is substantially higher than granular-flow surface, the lower part of the velocity profile in the flowing layer still obey SSH rheology. The upper part of velocity profiles near the free surface follow the Bagnold-type velocity profiles instead.